Energy efficiency is a key requirement for wireless sensor nodes, biomedical implants,
and wearable devices. The energy consumption of the sensor node needs to
be minimized to avoid battery replacement, or even better, to enable the device to
survive on energy harvested from the ambient. Capacitive sensors do not consume
static power; thus, they are attractive from an energy efficiency perspective. In addition,
they can be employed in a wide range of sensing applications. However, the
sensor readout circuit–i.e., the capacitance-to-digital converter (CDC)–can be the
dominant source of energy consumption in the system. Thus, the development of
energy-efficient CDCs is crucial to minimizing the energy consumption of capacitive
sensor nodes.
In the first part of this dissertation, we propose several energy-efficient CDC architectures
for low-energy sensor nodes. First, we propose a digitally-controlled coarsefine
multislope CDC that employs both current and frequency scaling to achieve
significant improvement in energy efficiency. Second, we analyze the limitations of
successive approximation (SAR) CDC, and we address these limitations by proposing
a robust parasitic-insensitive opamp-based SAR CDC. Third, we propose an
inverter-based SAR CDC that achieves an energy efficiency figure-of-merit (FoM)
of 31fJ/Step, which is the best energy efficiency FoM reported to date. Fourth, we propose a differential SAR CDC with quasi-dynamic operation to maintain excellent
energy efficiency for a scalable sample rate.
In the second part of this dissertation, we study the matching properties of small
integrated capacitors, which are an integral component of energy-efficient CDCs. Despite
conventional wisdom, we experimentally illustrate that the mismatch of small
capacitors can be directly measured, and we report mismatch measurements for subfemtofarad
integrated capacitors. We also correct the common misconception that
lateral capacitors match better than vertical capacitors, and we identify the conditions
that make one implementation preferable.
In the third and last part of this dissertation, we investigate the potential of novel
metal-organic framework (MOF) thin films in capacitive gas sensing. We provide
sensitivity-based optimization and simple fabrication flow for capacitive interdigitated
electrodes. We use a custom flexible gas sensor test setup that is designed and built
in-house to characterize MOF-based capacitive gas sensors.
| Identifer | oai:union.ndltd.org:kaust.edu.sa/oai:repository.kaust.edu.sa:10754/582481 |
| Date | 11 1900 |
| Creators | Omran, Hesham |
| Contributors | Salama, Khaled N., Computer, Electrical and Mathematical Sciences and Engineering (CEMSE) Division, Kosel, Jürgen, Eddaoudi, Mohamed, Sylvester, Dennis, Al-Attar, Talal |
| Source Sets | King Abdullah University of Science and Technology |
| Language | English |
| Detected Language | English |
| Type | Dissertation |
| Rights | 2016-11-22, At the time of archiving, the student author of this dissertation opted to temporarily restrict access to it. The full text of this dissertation became available to the public after the expiration of the embargo on 2016-11-22. |
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